Working up high

At 8,100 feet, Vail Valley is nestled in the Colorado Rocky Mountains and draws millions
of visitors a year. Recently, one of them, a 37-year-old man, walked into the local
ED complaining of frothy cough, fatigue, and dyspnea. The patient had arrived three
days earlier from sea level and immediately hit the ski slopes.

But after two days, he developed a dry cough and shortness of breath that did not
improve with rest. His symptoms worsened until he couldn't sleep. Physical examination
revealed tachypnea, tachycardia, and a room air pulse oximetry reading of 65%, but
no jugular venous distention or lower-extremity edema. Auscultation and chest X-rays
revealed diffuse wet crackles without wheezing through all lung fields and diffuse
alveolar infiltrates.

Photo by Thinkstock

This was a classic case of high-altitude pulmonary edema (HAPE), a noncardiogenic
form that occurs when lowlanders rapidly ascend to high altitudes and exercise vigorously
without allowing time to acclimate.

HAPE is only one of the conditions and factors that distinguish high-altitude hospital
medicine from practice at sea level. Hospitalists working up high have learned the
fine points of when to worry and take action and when to accept the normal responses
of the human body to increased elevation.

As is typical in HAPE, the patient improved dramatically after about 36 hours of supplemental
oxygen with a non-rebreather mask and twice-daily extended-release nifedipine (30
mg) to lessen his pulmonary hypertension, said Jamie Gray, MD, ACP Member, who has
practiced hospital medicine at Vail Valley Medical Center for the past 11 years.

HAPE can send patients to the hospital even if they are young and healthy, without
underlying cardiopulmonary disease, said Dr. Gray. While HAPE can resemble pneumonia,
affected patients usually have oxygen saturation, pulmonary exam, and chest X-ray
results that are “far out of proportion to their clinical picture,”
she added. “I become very suspicious of HAPE in the two- to five-day window
after arrival to altitude. A repeat chest X-ray at 24 hours showing near resolution
of the infiltrates with oxygen and nifedipine confirms the diagnosis.”

Acute illnesses

Acute altitude-related illnesses tend to begin as a constellation of nonspecific signs
and symptoms including headache, dizziness, gastrointestinal upset, fatigue, and sleep
disturbances. Together, these are called acute mountain sickness. A rapid rate of
ascent is the most important risk factor for this condition, explained Nicholas Kanaan,
MD, an emergency medicine physician at the University of Utah in Salt Lake City (elevation
4,200 feet).

Travelers to high regions can help prevent acute mountain sickness by not ascending
more than 1,500 feet in 24 hours, added Dr. Kanaan, who has worked in Nepal near Everest
Base Camp and completed a wilderness medicine fellowship that focuses on high-altitude
illnesses. “It can take an entire week to properly acclimatize to 15,000-feet
elevation,” he emphasized. “Do not ascend any further if you start feeling
symptoms of altitude illness.”

Individuals who don't follow this advice risk having their acute mountain sickness
progress to HAPE or its relative, high-altitude cerebral edema (HACE), as in the case
of a young Japanese ski racer whose nonspecific symptoms progressed until she reported
intermittent troubles with vision. Imaging showed cerebral edema classic for HACE,
said Mark A. Norden, MD, ACP Member, a hospitalist at St. Anthony Summit Medical Center
in Frisco, Colo. (elevation 9,100 feet).

“Descent to lower altitude resolved her symptoms,” said Dr. Norden,
noting that he and his colleagues also treat HAPE at least weekly. Most patients improve
with high-flow oxygen, but many remain “very hypoxic after initial treatment
and need to descend to a Denver-area hospital at lower altitude,” he added.

Chronic exacerbations

In addition to its effects on healthy people, high altitude can significantly worsen
chronic conditions. In a study of nearly 650 patients with moderate to severe obstructive
sleep apnea, periodic breathing at altitudes of 4,500 to 7,000 feet approximately
quadrupled the hourly number of apneic events and substantially complicated titration
of positive airway pressure therapy, investigators reported in the December 2011 Journal of Clinical Sleep Medicine.

“At higher elevations, diseases related to sleep apnea, such as right-sided
heart failure and pulmonary hypertension, are more common, have more significant sequelae
on the body, and are more likely to be refractory to therapy. This makes managing
them more challenging,” said Jacob Imber, MD, an assistant professor in the
department of internal medicine at the University of New Mexico in Albuquerque (elevation
5,300 feet).

Dr. Gray offered the example of a patient with stable New York Heart Association Stage
II congestive heart failure or minimally symptomatic chronic obstructive pulmonary
disease at sea level traveling to 8,100 feet. “Within 48 hours, they are likely
to end up in the hospital with worsening of their chronic condition,” she said.
Likewise, a patient who has rate-controlled atrial fibrillation at sea level but travels
to high altitude might end up hospitalized after developing atrial fibrillation with
rapid ventricular response, she added.

Hospitalists who work at altitude need to be extra-vigilant about oxygen supplementation
for patients with chronic obstructive pulmonary disease, interstitial lung disease,
pulmonary hypertension, and obstructive sleep apnea, Dr. Imber added. He often sees
patients who descend to Albuquerque from the mountains of New Mexico for treatment,
he said. “It's very important to ask where your patient lives to understand
how elevation may affect their illness. The amount of oxygen they require to maintain
oxygenation during their hospital stay may be inadequate when they return home.”

Even patients with occult pulmonary disease who can maintain adequate oxygen saturation
when breathing room air at sea level might not be able to do so at altitude, experts
noted. In one case, a heavy smoker from Louisiana was hospitalized in Albuquerque
with diverticulitis, said Dr. Imber. The patient had no pulmonary symptoms but needed
nasal cannula oxygen therapy to maintain adequate oxygenation. As a commercial trucker,
he was not allowed to use a supplemental oxygen tank on the job. He asked to be discharged
without a tank. Dr. Imber agreed but recommended that the patient follow up with his
primary care physician back home.

The lower effective oxygen percentage at altitude also can trigger sickle-cell crises,
experts said. Dr. Imber described a young woman from Florida who rarely had sickle-cell
crises at home but experienced three such exacerbations during her first four months
at the University of New Mexico. “Her options were 24-hour oxygen supplementation—this
did not appeal to her—or to transfer to a lower elevation,” he said.

Long-term residents

Elevation does not directly affect medication efficacy but can alter treatment, even
when hospital patients “live high” year-round. “At altitude,
the air is drier and the effects of the sun are intensified by a thinner atmosphere,”
said Dr. Kanaan. “As a result, the body experiences more insensible fluid loss,
and people can become more profoundly dehydrated.”

Patients can be dehydrated without having tachycardia or ketonuria, Dr. Kanaan noted.
Therefore, hospitalists who work at altitude are especially careful to assess hydration
status and use IV fluids when indicated. “If you have access to an ultrasound
machine, evaluating the inferior vena cava before and after passive leg raise will
help guide how fluid-responsive patients may be,” he said.

Another consideration is that stable acclimatized patients often can be discharged
without supplemental oxygen even if their oxygen saturation is somewhat low, said
Daniel A. Kovnat, MD, FACP, a hospitalist at Christus St. Vincent Medical Center in
Santa Fe, N.M. (elevation 7,200 feet). “It is not unusual for these patients
to be doing well with an oxygen saturation of 88% or 89%,” he said.

These residents of high-altitude areas may have lower blood bicarbonate levels and
lower pH on arterial blood gases, indicating an appropriate renal response to low-level
chronic respiratory alkalosis resulting from mild hyperventilation, Dr. Kovnat noted.
If their anion gap is normal, hospitalists should avoid overdiagnosing and overtreating
renal tubular acidosis in patients with vague symptoms or slight abnormalities on
blood chemistry, he said.

Conversely, however, long-term residents can develop acute mountain sickness or even
HAPE after returning from a long trip to sea level. “I myself had a version
of this after I came back to Santa Fe after an extended time at sea level,”
said Dr. Kovnat. “Soon after flying in, I went for an aggressive mountain bike
ride, only to find myself vomiting on the side of the trail, sick from the high altitude.”
Likewise, Dr. Gray has treated severe HAPE in a patient who grew up in Vail and returned
after attending college at sea level.

All these cases illustrate complexities that the experts said they often learned on
the job. “I knew nothing about practicing medicine at altitude when I first
moved to this hospital, but the learning curve was quick,” Dr. Gray noted.
Some conferences focus on altitude medicine, as do many research articles and other
opportunities for self-study, she said. “Generally, there is a wealth of information
in the medical community that has been treating patients at altitude for decades.”

Amy Karon is a freelance writer in San Jose, Calif (elevation 82 feet).

ACP Hospitalist provides news and information for hospitalists, covering the major issues in the field. All published material, which is covered by copyright, represents the views of the contributor and does not reflect the opinion of the American College of Physicians or any other institution unless clearly stated.